Axial washer for a gear-type pump comprising an axial washer of this type

ABSTRACT

An axial washer of a gear-type pump, in particular an internal gear pump, includes a seal which surrounds a pressure area of the axial washer. The seal is applied to the axial washer as a free-flowing bonding mass that bonds with the axial washer.

The invention relates to an axial washer for a gear-type pump and to a gear-type pump comprising at least one axial washer of this type in accordance with the features of the preambles of claim 1 or 4.

PRIOR ART

Axial washers of this kind for axial sealing and for gap compensation on both sides of the gearwheels of gear-type pumps are known. By way of example, attention is drawn to patent DE 196 13 833 B4, which has an internal gear pump with an axial washer on each side of the gearwheels thereof. The axial washer is held in such a way that it can move axially and is fixed in terms of relative rotation. On the outer side thereof, i.e. a side facing away from the gearwheels of the gear-type pump, the axial washer is subjected to pressure and is pressed by means of the inner side thereof, the side facing the gearwheels, against the gearwheels in order to seal off a discharge region of a pump space axially. The pump space is a circumferential segment between the two gearwheels in which the gearwheels do not mesh with one another and in which the gearwheels pump liquid in the circumferential direction from an intake side to a delivery side of the gear-type pump during the operation of the gear-type pump, i.e. when the gearwheels thereof are being driven in rotation. The discharge region is a region of the pump space in which a higher pressure prevails than on the intake side or in which the pressure rises to the pressure on the delivery side during the operation of the gear-type pump, owing to the pumping action thereof.

For the application of pressure, the known internal gear pump has a pressure area for each of the two axial washers thereof. The pressure area is a flat, crescent-shaped depression which extends across the discharge region of the pump space and communicates with the discharge region of the gear-type pump. The pressure area does not have to have exactly the shape and size of the discharge region of the pump space: normally the pressure area has a larger area than the discharge region of the pump space, with the result that the application of pressure from the outside results in a force which presses the axial washer inward against the sides of the gearwheels of the gear-type pump. The pressure area is sealed off by a seal which surrounds the pressure area. The seal rests in a groove which extends along an edge of the pressure area.

When a pressure is applied from the outside, in other words a pressure outside the pressure area acting on the seal of the pressure area is greater than that in the pressure area, there is the risk that the seal will be forced into the pressure area because the groove in which the seal rests is lower on the side of the pressure area by a depth of the pressure area than on the outer side, this having the effect that the seal is not as well supported on the side of the pressure area as toward the outside.

DISCLOSURE OF THE INVENTION

On its outer side, the axial washer according to the invention, having the features of claim 1, has a seal surrounding a pressure area. According to the invention, the seal is applied to the axial washer as a free-flowing and setting compound. For example, the compound is pasty for application and is applied to the axial washer by means of a nozzle which imparts the cross-sectional shape of the seal to the compound.

Using a nozzle outlet, the pressure area on the axial washer is circled, with the result that the compound, which is applied in the form of a strand or a bead, for example, and forms the seal after setting, surrounds the pressure area. As it emerges from the nozzle, the compound is viscous enough to retain its shape, i.e. both its path around the pressure area and its cross-sectional shape. After setting, the compound applied to the axial washer forms the seal, which surrounds the pressure area of the axial washer. As a result of the setting process, the compound forming the seal, and hence the seal, is joined materially, that is to say as though adhesively bonded, to the axial washer. The compound preferably sets so as to be rubber-elastic, thus forming a flexible seal.

“Setting” is intended to mean solidification of the free-flowing, e.g. pasty, compound to form the seal, irrespective of the solidification mechanism. As stated, the seal is preferably (rubber-)elastic after setting.

The invention has the advantage of good stability of the seal, especially also when subjected to pressure from the outside. Another advantage is the suitability of the seal according to the invention for automatic production and application to the axial washer, with the seal being applied, as described, to the axial washer as a pasty sealing compound by means of a nozzle, wherein the nozzle is guided over the axial washer, along the edge of the pressure area, by a robot or some other machine or, conversely, the axial washer is guided across the nozzle outlet. Mounting of the seal, i.e. insertion of a sealing ring into a groove at the edge of the pressure area, is eliminated. The risk that the seal will not rest in the groove in the manner envisaged during the assembly of the gear-type pump is likewise eliminated. It is also conceivable to apply the seal to the axial washer by means of an injection mold. The injection mold has the shape of the seal as a cavity and is clamped to the axial washer in order to injection-mold the seal, i.e. to apply the setting compound that forms the seal to the axial washer, with the result that the axial washer closes (covers) the cavity of the injection mold, and the setting compound can be injected into the cavity.

It is possible to provide the pressure area in the outer side of the axial washer and/or in an inner wall of a pump casing of the gear-type pump, between which and the gearwheels of the gear-type pump the axial washer is arranged. Claim 2 provides the pressure area on the outer side of the axial washer.

For good stability of the seal, claim 3 envisages that the seal is applied in a fillet or a groove which surrounds the pressure area. The fillet or groove supports the seal against the application of pressure parallel to the outer side of the axial washer, although a fillet supports the seal in only one direction.

Claim 4 relates to a gear-type pump having an axial washer of the kind explained above. The gear-type pump preferably has axial washers on both sides of its gearwheels. The pressure area can be provided on the outer side of the axial washer and/or on an inner wall of the pump casing between which and the gearwheels of the gear-type pump the axial washer is arranged. It is likewise possible for the free-flowing and setting compound which forms the seal after setting to be applied to the outer side of the axial washer and/or to the inner wall of the pump casing, there also being the possibility of applying the seal to the axial washer and providing the pressure area on the inner wall of the gear-type pump or vice versa.

claim 5 envisages that the gear-type pump is an internal gear pump.

In particular, the gear-type pump according to the invention is provided as a hydraulic pump for delivering brake fluid in a hydraulic, slip-controlled and/or independently powered vehicle brake system. Although not necessarily applicable, such pumps are often referred to as return pumps.

BRIEF DESCRIPTION OF THE DRAWING

The invention is explained in greater detail below by means of an illustrative embodiment shown in the drawing, in which:

FIG. 1 shows a side view of a gear-type pump according to the invention without the pump casing;

FIG. 2 shows an axial section along the line II-II in FIG. 1; and

FIG. 3 shows a view of an axial washer according to the invention for the gear-type pump in FIGS. 1 and 2.

EMBODIMENT OF THE INVENTION

The gear-type pump 1 according to the invention, which is shown in FIGS. 1 and 2, is an internal gear pump and is provided for use as a hydraulic pump for producing a hydraulic brake pressure in a hydraulic slip-controlled and/or independently powered vehicle brake system (not shown). Although not necessarily applicable, such hydraulic pumps for vehicle brake systems are also referred to as return pumps. The gear-type pump 1 has two intermeshing gearwheels 2, 3, namely an externally toothed gearwheel, referred to here as pinion 2, and an internally toothed annulus 3. The pinion 2 is fixed for conjoint rotation on a pump shaft 4; it can be driven in rotation by the rotary drive of the pump shaft 4 and, for its part, drives the annulus 3 in rotation, said annulus being provided with sliding support for rotation in a bearing ring 5.

The gearwheels 2, 3 delimit a crescent-shaped pump space 6 between them, in which a crescent-shaped divider 7 is arranged to divide the pump space 6 into an intake region 8 and a discharge region 9. A pin 10, which passes transversely through the pump space 6, holds the divider 7, and the divider 7 is pivotable on the pin 10. Tooth tips of teeth of the gearwheels 2, 3 rest against an outer and an inner side of the divider 7 and slide along the outer and the inner side of the divider 7 when the gearwheels 2 and 3 are driven in rotation. During operation of the gear-type pump 1, i.e. when the gearwheels 2, 3 are driven in rotation, the gearwheels 2, 3 pump brake fluid or, more generally, fluid which is enclosed in interspaces between the teeth thereof from the intake region 8 to the discharge region 9, i.e. from an inlet to an outlet of the gear-type pump 1. An inlet bore 11 opens into the intake region 8, and a pump outlet is formed by a slot 12 in an axial washer 13, which will be explained below.

For axial sealing of the pump space 6, the gear-type pump 1, which is designed as an internal gear pump, has an axial washer 13 on each of the two sides of the gearwheels 2, 3. Where the edges 17, 18 of the axial washers 13 are concealed by the gearwheels 2, 3, the edges 17, 18 are indicated by dashed lines in FIG. 1. FIG. 3 shows an outer side of one of the two axial washers 13. The axial washers 13 are situated in an interspace between the gearwheels 2, 3 and the inner walls 14, 15 of a pump casing 16. The axial washers 13 cover at least the discharge region 9 of the pump space 6; in the illustrative embodiment, the axial washers 13 have the shape of circular segments which occupy more than the area of the semicircle and have a recess 19 in the form of an oblique step at a transition from a circular edge 17 to a straight edge 18 extending in the direction of a chord. The axial washers 13 have a hole 20 for the pump shaft 4 and a hole 21 for the pin 10 which holds the crescent-shaped divider 7. The axial washers 13 can move in the axial direction and are held in a manner fixed against relative rotation by the pump shaft 4 and the pin 10. By means of their inner sides, which face the gearwheels 2, 3, the axial washers 13 rest against the sides of the gearwheels 2, 3 and of the crescent-shaped divider 7 and seal the pump space 6 off at the sides.

On the outer sides, which face away from the gearwheels 2, 3, the axial washers 13 each have a pressure area 22. This is a flat, crescent-shaped depression in the outer sides of the axial washers 13 which extends from a central region of the divider 7 across the discharge region of the pump space 6. On the outside, the pressure area 22 reaches almost as far as the circular edge 17 of the axial washer 13 and, on the inside, almost as far as the hole 20 for the pump shaft 4. The pressure area 22 is surrounded by a groove in which there is a seal 23. The seal 23 is applied as a free-flowing pasty compound into the groove in the axial washer 13 surrounding the pressure area 22, being shaped in the process, before the gear-type pump 1 is assembled. The compound is applied by means of a nozzle (not shown), the nozzle outlet of which is moved along the groove to apply the compound. The nozzle has a shaping function, imparting its cross-sectional shape to the compound insofar as the latter projects from the groove. During application into the groove in the axial washer 13 surrounding the pressure area 22, the compound is viscous enough to retain the shape and cross section imparted to it by the nozzle. In the illustrative embodiment, the compound projects in the form of a bead with a semicircular cross section from the groove, beyond the outer side of the axial washer 13. The groove surrounding the pressure area 22 in the outer side of the axial washer 13 supports the free-flowing compound and simplifies the production of the seal by reducing the risk that the compound will flow away. The setting process joins the seal 23 materially to the axial washer 13. After setting and the assembly of the gear-type pump 1, the seal 23, which, as already stated, projects in the form of a bead somewhat above the outer side of the axial washer 13, rests against the inner wall 14, 15 of the pump casing 16 and seals off the pressure area 22 at the inner wall 14, 15. One inner wall 14 is formed by a bottom of a stepped recess in the pump casing 16, into which the gear-type pump 1 is installed. The other inner wall 15 is formed by an inner side of a casing cover 24 which closes the pump casing 16.

Within the pressure area 22, the axial washer 13 has the arc-shaped slot 12 already mentioned, which passes through the axial washer 13. The slot 12 is situated in the discharge region 9 of the pump space 6, and therefore the pressure area 22 communicates with the discharge region 9 of the gear-type pump 1, which is designed as an internal gear pump. The pressure areas 22 of the axial washers 13 are thus subjected to the pressure which prevails in the discharge region 9 of the gear-type pump 1, i.e. to the pressure of the pump outlet. This pressure acts on the outer sides of the axial washers 13 and presses the inner sides thereof into sealing contact with the gearwheels 2, 3 and the divider 7 of the gear-type pump 1, thereby ensuring the lateral sealing of the pump space 6 in the discharge region 9. The discharge region 9 communicates via the slot 12 in one of the two axial washers 13 with an outlet bore 25 in the pump casing 16.

By means of the shaping application of the seal 23 as an initially pasty compound, which sets in the groove in the axial washer 13 surrounding the pressure area 22 to form the flexible seal 23, the seal 23 is joined materially to the axial washer 13. The seal 23 is provided with additional stability by being applied into the groove surrounding the pressure area 22.

In the illustrative embodiment, the pump casing 16 is part of a hydraulic block of a slip control system (not otherwise shown) of a hydraulic vehicle brake system. Apart from the gear-type pump 1, which forms a hydraulic pump of the slip control system, additional hydraulic components, such as solenoid valves, are inserted into the hydraulic block forming the pump casing 16 and hydraulically interconnected. Hydraulic blocks of this kind are known to a person skilled in the art, and will not be explained specifically here. To fill the vehicle brake system, said system is initially evacuated in order to avoid air inclusions. Brake fluid is then introduced. During this process, the seal 23 of the pressure area 22 may be subjected to pressure from outside, i.e. the pressure on the outside may be higher than that in the pressure area 22. Because the seal 23 is applied with a shaping action and, as a result, is joined materially to the axial washer 13, it withstands such an application of pressure from the outside. In addition, stability is imparted to the seal 23 by the groove surrounding the pressure area 22, in which the seal 23 is situated.

Instead of being provided in the outer side of the axial washers 13, the groove with the seal 23 and/or the pressure area 22 can be provided in the inner walls 14, 15 of the pump casing 16, and the seal 23 can also be provided in the outer side of the axial washer 13 and the pressure area 22 in the inner wall 14, 15 of the pump casing 16 or vice versa. It is also possible to provide the pressure area 22 and/or the seal 23 both on the outer side of the axial washers 13 and on the inner walls 14, 15 of the pump casing 16 (not shown).

The pump shaft 4 is provided with sliding support in the pump casing 16 and in the housing cover 24 by means of two bearing bushes 26 on both sides of the gearwheels 2, 3, and is sealed off in the housing cover 24 by means of a seal 27. 

1. An axial washer for a gear-type pump, comprising: an axial washer body having an outer side; and a seal surrounding a pressure area on the outer side, the seal is being applied to the axial washer body as a free-flowing and setting compound which, after setting, forms the seal and is joined materially to the axial washer body.
 2. The axial washer as claimed in claim 1, wherein the axial washer body has the pressure area.
 3. The axial washer as claimed in claim 1, wherein the seal is applied in a fillet or a groove which surrounds the pressure area.
 4. A gear-type pump, comprising: two meshing gearwheels; an axially movable, rotationally fixed axial washer configured to laterally seal a discharge region of a pump space between the gearwheels; a pressure area on an outer side of the gearwheels, said outer side facing away from the gearwheels, the pressure area communicating with the discharge region such that, when subjected to pressure from the outside, the axial washer is pressed against one side of the gearwheels of the gear-type pump; and a seal surrounding the pressure area, the seal is being applied as a free-flowing and setting compound to the axial washer or to an inner wall of a pump casing of the gear-type pump facing the axial washer, wherein, after setting, the free-flowing compound forms the seal and is joined materially to the axial washer or to the inner wall of the pump casing.
 5. The gear-type pump as claimed in claim 4, wherein the gear-type pump is an internal gear pump. 